The present invention is directed to a blood extraction device as described hereinafter, and in addition, a procedure for using it, and a device for execution of a procedural step in the use of the blood extraction device.
Blood extraction devices are generally known, for example see U.S. Pat. Nos. 2,460,641 and 3,136,440. In the prior art, the seal of the blood sample tube consists of a rubber stopper. If this stopper is opened in order to remove the extracted blood for further use or analysis, a certain momentary low pressure will occur at the surface of the blood sample, with the result that some drops of the blood sample may be scattered when the stopper is removed. This "aerosol" effect is reinforced by the elasticity of the stopper material when it is opened rapidly. The danger of this "aerosol" effect may be particularly grave if the inside surface of the stopper is covered by test liquid due to sequential handling of the blood sample tube; in such a case, individual droplets are figuratively thrown off the surface when the stopper is rapidly opened. This effect may have inherent infection risks. The staff member comes into contact with a patient's blood, which may be infected. It is also a major consideration that in this manner, cross-contamination of samples may occur in the laboratory. For this reason, stopper removers have been specifically developed as separate devices. However, to utilize a specific tool for opening the sample tubes is impractical, even if the clinic staff does become accustomed to this procedure.
Since, in the case of the known devices, the vacuum is created already in the production stage, the seal must be designed so that it maintains the vacuum for a longer period of time. The rubber stopper must be thick at the edge. Frequently, penetration by a hollow needle requires too much force. For this reason, a recess is provided in the center of the stopper, in order to have a thinner place for penetration. Thus, the needle cannot be inserted close to the side, i.e. eccentrically, which would be desirable in order to make a "flatter" insertion into the patient's vein. Furthermore, in the case of known tubes, there may be the disadvantages that according to the age of the tube, the initially uniform vacuum may have decreased so that there is no guarantee of constant and uniform speed of blood extraction, nor for a constantly uniform volume of the extracted sample.